While the prevailing winds in California come from the west off the cool Pacific ocean, the Santa Ana blows from the east and comes from the high, dry desert plateaus of the mountain ranges east of Los Angeles and San Diego. More than just a dry mountain breeze; a Santa Ana is a hot, powerful wind that can quickly turn small brush fires into unstoppable infernos.

The Santa Ana is a special type of wind, known as a katabatic wind, well known in other parts of the world. In parts of the American West, this wind is called the Chinook; in southern France it is called the Mistral; in Japan it's the Oroshi; and in Austria and Germany it is called the Foehn.

Here's how the wind is created (it's not from Glen Campbell's singing).

First, air tends to pool at high elevations, where it cools. As winds pass over the top of the mountains, water-like eddies form and some air breaks away from the main wind stream, where it pools and cools.

Second, a weather condition that will cause this cooled air to spill down from its high-elevation position is required—typically a high pressure in the northern Rocky Mountains. The clockwise air circulation of this high pressure system forces the winds downward from the high plateau. Once the air is dislodged from its high elevation, it sinks rapidly since it is cooler—and more dense—than the surrounding air below.

As it sinks, the third factor cones into effect: air pressure increases, which compresses the cool, dry air. As it's compressed (it's called adiabatic compression), the air temperature increases at a rate of 29°F per 5000 feet of elevation).

Now the fourth factor comes into play. As the air warms it tries to expand. often, though, the downslope winds are foreced between mountains that form natural venturis and force the winds down through valleys, increasing the wind speed.

What began as cool, dry air pulled down by gravity becomes hot dry wind propelled by the increasing pressure of the air as it heats up, the fifth and final factor.

These winds can commonly reach speeds of 25-35 miles per hour, often exceed 60 miles per hour, and has been known to reach 200. Hot, dry winds traveling at such speeds are enough to whip common brush fires into intense, region-wide fires that can scorch thosuands of acres of Southern California.

Comments

Popular posts from this blog

Foolishness! Your DNA would actually stretch to the sun and back about 4 times!

DNA is a fine, spirally coiled thread in the nucleus of every living cell that serves as a guidebook so the cells "know" what they're supposed to do. The strands are so fine you need a high power electron microscopes to see them.

The human genome, the genetic code in each human cell, contains 23 DNA molecules each containing from 500 thousand to 2.5 million nucleotide pairs. DNA molecules of this size are 1.7 to 8.5 cm long when uncoiled, or about 5 cm on average.

You have about 10 trillion cells in your body, so if you stretched the DNA in all the cells out, end to end, they'd stretch over 744 million miles. The moon is only about 250,000 miles away, so all your DNA would stretch to the moon and back alomst 1500 times. The sun is 93,000,000 miles away, so your DNA would reach there and back about 4 times!

Interestingly, no more than 1.5 percent of the human genome contains DNA that help…

Really. Or to use a more “explosive” illustration, multiply the world’s entire nuclear stockpile seven million times and detonate it. That’s also about one second’s solar output. Or put another way … well, you get the point; the Sun puts out a lot of energy.

We only avoid being incinerated by this 800,000 mile wide, 100,000,000 degree inferno because, like a light bulb, the Sun radiates in every direction. That, and the fact that we are 93,000,000 miles away, allows us to experience sunshine as a gentle blessing rather than an incinerating white-hot blast.

But where does so much energy come from? That question stumped scientists from the late 1800’s until the early 1900’s. By then science had come to realize that the earth was billions of years old, not just thousands as previously believed. But they couldn’t figure out what could have powered the Sun that energetically for so long.

The general answer came with the new science of nuclear physics and with Einstein’s postulation of his fam…

Really. The top of towers of the Verrazano - Narrows Bridge at the mouth of the Hudson river in New York City are tilted almost two inches further apart than the base thanks to the curve of the Earth's surface.

Actually, there are a lot of amazing things about that not-so-famous bridge.

When it opened in 1964, at 4260 feet it was the longest suspension bridge in the world, exceeding the Golden gate completed in 1937, by 60 feet. Today it's the longest single span in North America and the seventh longest in the world. (The longest is the 6,529 foot Akashi-Kaikyo Bridge in Japan, completed in 1998.)

The Verrazano - Narrows Bridge contains enough concrete to construct a single lane highway from New York to Washington, and if the wires that make up the suspension cables were laid end-to-end they would reach 143,000 miles, more than halfway to the moon.

On hot days, the double-decker road bed expands almost six feet and sags 12 feet lower, something that ships passing underneath have …